Many single-wafer processing systems use substrate holders, such as an electrostatic chuck in combination with a base, to retain a wafer during semi-conductor substrate processing. A backside purge gas, flowing between, for example, the wafer, and the electrostatic chuck (also referred to as an “echuck”), is used to regulate the temperature of the wafer. The backside gas is typically used as a heat transfer medium. As voltage is applied to an electrostatic chuck, a coulomb force holds the wafer in place. In some instances, the coulomb force might be of the Johnson-Rahbek variety. Often, during processing of the wafer, contaminants and/or debris sputter from the wafer and adhere to the electrostatic chuck. Contaminants or debris includes materials that are foreign to the chuck, that is, materials that have come from a source other than the chuck and that interfere with the operation of the chuck when present in sufficient amounts. During ion implantation, for example, organic materials such as photo resist may dislodge from the wafer and adhere to the chuck. During repeated film fabrication process in a process chamber, contaminants will adhere to, and build up on, the electrostatic chuck. These contaminants that adhere to the electrostatic chuck include, primarily, organic materials, etc., that were originally on the semiconductor wafers themselves. When there is a buildup of this type of contaminant, the strength with which the electrostatic chuck is able to chuck and secure the semiconductor wafer is weakened, which may cause the wafer to shift out of position. Thus, the presence of debris on the chuck interferes with chucking and de-chucking of the substrate. Moreover, the build-up of debris on the chuck impacts the ability to maintain a low operating pressure of approximately 10−6 torr in the ion implantation system.
Typically, when a chuck has become too dirty to effectively retain a wafer, the process must be shut down, so that the chuck can removed and cleaned. Cleaning the chuck generally involves an aggressive cleaning with stripping chemicals, which can reduce the useful life of the chuck. Moreover, shutting down the process itself is disruptive and inefficient, for example, throughput is reduced.
There is a need, therefore, to provide apparatus and methods for cleaning electrostatic chucks that minimize disruption to substrate processing.